The communication facilities enjoyed by the crew of the Jupiter 2 in Lost in Space are not notably futuristic. This, however, should not be taken to imply that what was portrayed in the series was not at least on the cutting edge of technology available in the 1960’s; rather, in the field of communications at least, there seems to have been little effort made to extend the possibilities of contemporary technology a generation into the future.
Hand-held walkie-talkies (sometimes simply called radios by the characters) appear frequently. The only somewhat detailed view we have of one is in the episode “Return from Outer Space” where we are afforded a very brief look at Will’s radio before it is damaged. The character Davey makes an apt observation that it looks like a dime-store toy: it does. It is also rather bulkier than the walkie-talkies seen in other episodes; in “Castles in Space” Don is seen using one that is both smaller and more traditional looking.
Both the Robot and spacesuit helmets have built in communications systems. Communication with a crew member engaged in extra-vehicular activity or with the Robot is accomplished using hand-held microphones. Oddly enough, on the occasions when someone wants to know where the Robot is, it never seems to occur to anyone to call him.
The microphones most frequently seen in use are on the main control console on the upper deck, at what seems to be a more dedicated communications installation between the control console and the air lock, and at another panel midway between the airlock and the lift. There is also a jack near the airlock. In one episode, Maureen is seen using a microphone in front of the airlock; unfortunately, the cord is seen hanging free; apparently its effectiveness is not impaired when not plugged in. The microphones are also used to communicate between the upper and lower decks; there is a microphone installed near the sleeping quarters.
There are several references to relay stations being built and maintained over the series. Any cell phone user can quickly appreciate the need for these. The stations create a bit of a conundrum; to be effective at all (assuming the Robinsons have not launched a communications satellite) they must be in line of site with each other, yet these installations are often implied to be at some distance from the Jupiter 2. In addition, they would only be necessary if the planets they were on lacked an ionosphere (very unlikely) or if there were hills of moderate height near the Jupiter 2 to block line of sight communication. The landing site of the Jupiter 2 on the Sector 6:30 planet is in fact described as being in a hollow (“The Forbidden World”), but on Priplanus, despite the occasional long establishing shot of the area of the Jupiter 2, there do not seem to be any such features near-by (despite the regular appearance of mountains in the early episodes).